“Clear sea water color”, this is how it appears written on the historic tag that accompanies the exceptional single crystal of beryl illustrated in the figure. Beryl - whose name, not surprisingly, derives from the Greek beryllos and means "precious blue-green sea water" - is a mineral famous for its well-known gemological varieties: emerald (green color) and aquamarine (blue color) . For this reason, the great majority of beryl crystals that have a color, transparency and clarity such as to be used in the gemological field are cut and removed from the mineralogical collections. A splendid exception is this sample, extracted in Siberia, and arrived in the Museum of Mineralogy of Sapienza with the acquisition of the Spada collection in 1852; the crystal in question is characterized by an intense blue-greenish color, by an exceptional transparency and by an excellent clarity. Only the stubborn conservation work of Monsignor Lavinio de 'Medici Spada and the successive directors of the Museum has allowed this crystal to "survive" the pressure of the jewelers and keep all its splendor intact.

Few specimens in the world are able to represent the mineral beryl as this Siberian crystal; it is sufficient to visit the showcase where it is exhibited and admire the light it releases to understand why the Latin term berillus, abbreviated to the prefix brill-, gave rise to the Italian verb “to shine”.